An apically located hybrid guanylate cyclase-ATPase is critical for the initiation of Ca2+ signaling and motility in Toxoplasma gondii

Luning Yang, Alessandro D. Uboldi, Simona Seizova, Mary Louise Wilde, Michael J. Coffey, Nicholas J. Katris, Yoshiki Yamaryo-Botté, Martina Kocan, Ross A.D. Bathgate, Rebecca J. Stewart, Malcolm J. McConville, Philip E. Thompson, Cyrille Y. Botté, Christopher J. Tonkin

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6 Citations (Scopus)


Protozoan parasites of the phylum Apicomplexa actively move through tissue to initiate and perpetuate infection. The regulation of parasite motility relies on cyclic nucleotide-dependent kinases, but how these kinases are activated remains unknown. Here, using an array of biochemical and cell biology approaches, we show that the apicomplexan parasite Toxoplasma gondii expresses a large guanylate cyclase (TgGC) protein, which contains several upstream ATPase transporter-like domains. We show that TgGC has a dynamic localization, being concentrated at the apical tip in extracellular parasites, which then relocates to a more cytosolic distribution during intracellular replication. Conditional TgGC knockdown revealed that this protein is essential for acute-stage tachyzoite growth, as TgGC-deficient parasites were defective in motility, host cell attachment, invasion, and subsequent host cell egress. We show that TgGC is critical for a rapid rise in cytosolic [Ca2+] and for secretion of microneme organelles upon stimulation with a cGMP agonist, but these deficiencies can be bypassed by direct activation of signaling by a Ca2+ ionophore. Furthermore, we found that TgGC is required for transducing changes in extracellular pH and [K] to activate cytosolic [Ca2+] flux. Together, the results of our work implicate TgGC as a putative signal transducer that activates Ca2+ signaling and motility in Toxoplasma.

Original languageEnglish
Pages (from-to)8959-8972
Number of pages14
JournalThe Journal of Biological Chemistry
Issue number22
Publication statusPublished - 31 May 2019


  • calcium
  • Toxoplasma gondii
  • cell motility
  • cyclic GMP (cGMP)
  • cyclic nucleotide

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